A wind power generator system includes a speed increasing gear for increasing the speed of a rotary shaft connected to the rotor of the windmill to drive the generator. Since relatively large radial loads tend to be applied to the torque transmission mechanism of such a wind power generator system, the rotary shaft and the torque transmission shaft in the speed increasing gear are rotatably supported by cylindrical roller bearings which are large in load capacity.
Today, it is increasingly required that cylindrical roller bearings have a long life when used under further heavier loads. This requirement is fulfilled by increasing the size of the cylindrical rollers, or increasing the number of the cylindrical rollers. However, either of the above solutions narrows the distances between the adjacent cylindrical rollers on the pitch circle of the cylindrical rollers. This makes it necessary to reduce the widths of the pillars of the retainer, which in turn raises a concern regarding the strength of the retainer.
A full type cylindrical roller bearing, i.e. a bearing having no retainer, which is disclosed in JP Patent Publication 9-88970A, is large in load capacity and is suitable for use under heavy loads. However, since this type of bearing has no retainer, its rotation properties are not good, and also, damage to the surfaces of the cylindrical rollers is concerned because the cylindrical rollers contact each other while rotating.
JP Patent Publication 2008-03893A discloses a cylindrical roller bearing of which the pillars of the retainer is located radially inwardly or radially outwardly of the pitch circle of the cylindrical rollers. By locating the pillars of the retainer offset from the pitch circle of the cylindrical rollers. As a result, it is possible to increase the size of the cylindrical rollers or increase the number of the cylindrical rollers, which in turn makes it possible to increase the load capacity of the cylindrical roller bearing while maintaining good rotation properties.
The cylindrical roller bearing disclosed in JP Patent Publication 2008-03893A includes a bearing race having two flanges, and a bearing race having one flange. Since the retainer is disposed between these bearing races so as to be offset from the pitch circle of the cylindrical rollers toward the bearing race with two flanges, if the bearing race with a single flange is separated from the bearing, the cylindrical rollers are also separated such that the bearing becomes completely disassembled. Thus, it is extremely troublesome to assemble this cylindrical roller bearing.
In order to prevent separation of the bearing race with a single flange, it is necessary to mount a snap ring at the end of a cylindrical raceway of the bearing race with a single flange. However, since a snap ring is insufficient in strength, it is difficult to guide the end surfaces of the rollers with a snap ring.